Isobutanol is produced naturally during the fermentation of carbohydrates and may also be a byproduct of the decay process of organic matter (Atsumi et al. 2008 Nature 451:86-89). The biosynthetic pathway used to produce isobutanol was first discovered in species of bacteria from the genus Clostridium. This pathway has been genetically engineered into several species of microorganisms which are more easily manipulated by current scientific methods than microorganisms of the genus Clostridium (Peralta-Yahya et al. 2012 Nature 488: 320-328).